Apparatus for controlling a continuous rolling mill to maintain constant gage in theleading and trailing ends of strip lengths



1964 R. w. HOLMAN ETAL 3,151,503

APPARATUS FOR CONTROLLING A CONTINUOUS ROLLING MILL T0 MAINTAIN CONSTANTGAGE IN THE LEADING AND TRAILING ENDS 0F STRIP LENGTHS Filed June 23,1955 2 Sheets-Sheet 1 INVENTORS.

ROBERT W HOLMAN and JAMES E. Mc NAMARA,

AmuA/ozem their Attorney.

3,151508 CGNTROLLING A CONTINUOUS ROLLING MAINTAIN CONSTANT GAGE Gci.'5, 1964 R. w. HOLMAN ETAL APPARATUS FOR MILL TO IN THE LEADING ANDTRAILING ENDS OF STRIP LENGTHS 2 Sheets-Sheet 2 Filed June 23, 1955 YINVENTORS ROBERT m HOLMANand -JAME$ E. Mc NAMARA,

their Attorney.

United States Patent APE'ARATUS rota cor irrihrrnto a courmooos ROLLTNGM'EL hlAlNTAIN CSNSTANT GAGE ZN TEE AND TRAELYING 9? STAR? LENGTHSRobert W. Holman, Pittsburgh, and ames E. McNamara,

Bridgeville, Pa, assignors to United States Steel iorporation, acorporation or" New .l'erse Filed dune 23, 1955, Ser. No. 5117,5134- 17(Ql. till-) This invention relates to the cont nuous hot-rolling ofmetal and, more particularly, to the con rol of the several stands of arolling mill in order to maintain a constant gage in the leading andtrailing ends of strip length Specifi ally the invention relates to acontrol system for the motors of a continuous mill for rollingbreakdowns into strip, whereby the ed of the second and each subsequentmill stand of the finishing train is reduced temporarily as the leadingend or" a breakdown approaches it and again as the trailing end of thebreakdown leaves the preceding stand. The effect of such control is toreduce the abnormally heavy tension to which the leading end issubjected on entering successive stands, thereby preventing an excessivereduction of the leading. end as a result or" the added tensionotherwise existing. A further effect is to prevent an increase inthickness at the trailing end of the breakdown as a result of the lossof tension which would otherwise occur, by increasing the tension onthat portion thereor between the second and third stands, after thetrailing end leaves the first stand, and so on.

When a breakdown rolled from a hot slab in the roughing train of acontinuous mill is put through the finishing train of the mill to reduceit to a strip or" predetermined gage, there is usually a gradualincrease in the strip thickness above that which should be maintained atany stage of the rolling, because the breakdown is being rolled atcontinuously decreasing temperatures. Usually, furthermore, there is anappreciable amount or tension on the strip as it passes through thefinishing train, and there will also be rapid changes in thickness asthe head end of the breakdown enters the finishing train andas thetrailing end leaves The increase in finished thickness at the trailingend is more serious. This invention relates to means for eliminating thechan s of thickness of the finished strip resulting from vary ngtension.

The motors driving the finishing stands of a hot-strip mill are usuallydesigned with drooping speed characteristics, i.e., the motor speed willdecrease with increasing load, to the extent of two percent or more,from no load to full load. The finishin train is thus stable and easilycontrolled since the overall system tends to be self-regulating. if, atany instant, the mill stand speeds are not exactly proportional relativeto the desired percentages of strip reduction at each stand, the standwhich is running too fast will increase tension at the input side andrelax tension at the output side, thus increasing its motor load whichwill cause the speed to decrease, thereby tending to correct theunbalanced tension conditions. This stand which is running too fast willalso affect the preceding and succeeding stands in a manner which willstabilize the system, since an overhauling load will be transmitted bytension to the preceding stand, thus causing it to speed up and relaxtension, and the load on the succeeding stand will decrease because itsback tension has been relaxed and it will therefore speed up to againestablish tension. Thus the system is stable and does not require exactpresetting of motor speeds and roll positions and continual adjustmentsto meet strip conditions, as would be required if the drive motors weredesigned with flat speed characteristics.

Patented Get. 6, 1964 ice Usually the operator will adjust each motor tooperate on no-load at a speed slightly higher than anticipated rollingspeed so that under normal rolling conditions, a motor will not causethe strip to form a loop on the entry side of a mill. trip tension willbe established when the strip is in the mill, furthermore, after motorspeeds have decreased in accordance with their speed characteristicsdescribed above. As the breakdown enters each stand, however, the motoris initially running faster than its full-load speed. Because of thelarge inertia of each mill stand and drive motor, the slow-down frominitial or no-load speed to full-load or normal rolling speed cannot beinstantaneous and the head end of the breakdown, in causing thisslow-down, is subjected to excessive tension as it enters each stand,depending on the amount or" speed differential, motor speed regulationand the time constants of the system. When the initial se -up of themill is such that tms over-tension condition will exist, the finishedthickness at the head end will be less than desired and there will bevariations in the finished thickness over a length of finished stripwhich is equivalent to the volume of strip between the first and laststand. Stable rolling conditions thus established continue until thetrailing end of the strip starts to leave he finishing mill stands.

When the trailing end of the breakdown leaves the first stand there is aloss of tension on the portion thereof between the first and secondstands, and the strip enters the second stand at a thickness greaterthan during normal rolling. Because of the elasticity of the millhousings, the thickness of the strip at the delivery side of the secondstand will immediately increase. As the trailing end leaves the secondstand, there is loss of tension on the portion of the breakdown betweenthe second and third stands. Consequently, the thickness of the strip atthe output side of the third stand will increase immediately. Thisincrease in thickness is progressive as the strip leaves each millstand. These individual losses of tension will result in a progressiveincrease in finished thickness over a length of finished stripequivalent to the volume of metal in the portion of the breakdownbetween the first two stands. There is an additional efiect of loss oftension reflected through the mill as discussed below.

When the trailing end of the strip leaves the first stand and tension islost on the breakdown portion between the first and second stands, theload on the second stand decreases somewhat, depending on the amount oftension previously maintained between the first two stands and thesecond stand will speed up slightly because of the speed characteristicof its motor. This results in an 'mrnediate decrease in tension betweenthe second and third stands, which decreases the load on the thirdstand, thus decreasing tension between the third and fourth stands. Inthis same manner, tension decreases between the fourth and fifth standsand between the fifth and sixth stands. Thus, loss of tension betweenthe first and second stands results in an immediate decrease in tensionbetween the fifth and sixth stands and the thickness of the finishedstrip will increase. This reflected loss of tension and resultingincrease in thickness occurs as the trailing end of the strip leaveseach stand. Therefore, if strip tension is established through thefinishing train and the main drive motors have drooping speedcharacteristics, the th ckness of the finished strip will start toincrease as soon as the trailing end leaves the first stand and willincrease progressively as the trailing end leaves each stand. The amountof increase in thickness depends on the amount of tension previouslyestablished.

There are thus two effects of tension on the thickness of the finishedstrip at the trailing end; one, the individual loss of tension betweenadjacent stands, and the other,

' illustrating the present preferred embodiment.

3 the reflected decrease in tension between the last two stands. Thisincrease in thickness at the trailing end has been observed to be asmuch as 10%, which can result in considerable waste product and increasethe manufacturing difiiculties encountered in processes subsequent tothe hot-rolling operation. This invention relates to a system of controlto alleviate these efiects of tension on finished thickness. The controlwill operate in such a manner as to decrease temporarily the speed ofthe main drive motors of the second through the fifth stands as thebreakdown enters each immediately preceding stand and again as thebreakdown leaves the preced ing stand. 7

We accomplish this object by providing means responsive to the passageof the leading end of a breakdown through the first stand of a finishingtrain for example, efiective to superimpose a temporary supplementalcontrol on the speed of'the motor driving the second stand, to slow itdown temporarily so it will not exert excessive tension in being slowedby the work to normal running speed. The control is removed as normalrolling conditions are achieved. Similarly, the temporary speedreduction is applied to the second stand when the trailing end leavesthe first stand. The resulting increased tension causes the trailing endto be reduced more than it otherwise would be, thereby compensating forthe thickening effect which would normally occur as above described. Thetemporary supplemental speed control applied first to the motor of thesecond stand is later applied to the motor of the third stand when theleading end enters the second stand and again when the trailing endleaves it and so on.

A complete understanding of the invention may be obtained from thefollowing detailed description and explanation which refer to theaccompanying drawings In the drawings:

FIGURE 1 is a diagrammatic showing of the first two stands in thefinishing train of a continuous hot-strip mill, the motors driving themand some of the auxiliary control devices;

FIGURE 2 is a circuit diagram showing the speed control means providedfor each of the motors of the second and succeeding stands; and

FIGURE 3 is a schematic circuit showing the control relays for bringingthe control means of FIGURE 2 into operation at the proper times.

Referring now in detail to the drawings, and for the present to FIGURE1, mill stands 1 and 2 are driven by motors 3 and 4 respectively. Thesestands are the first two of, for example, a six-stand finishing trainfollowing a roughing train of four stands (not shown). A tachometergenerator 5 is driven by motor 4. The speeds of motors 3 and 4 aremanually controlled by motordriven main field rheostats 6 and Vernierrheostatsida, only 'those for motor 4 being shown in FIGURE 1.Supplemental control of the excitation of .motor 4 is effected by aregulator 7. The motor 4 normally operates at a speed somewhat greaterthan that of motor 3 because of the elongation of the breakdown 8effected in stand 1, and the need to maintain the portion thereofbetween the stands under tension to aid the reduction. This tension isabnormally high when the leading end of the breakdown enters stand 2running at no-load speed. The tension on this trailing end is relieved,however, the instant it leaves the stand 1, so far as the portion of thebreakdown between stands 1 and 2 is concerned.

Motor-field regulator 7 is controlled by a speed-follower potentiometer10 and tachometer generator 5. A speed-follower regulator 9 controls amotor 11 which drives potentiometer 10. Regulators 7 and 9 areArnplidyne generators driven by a motor 12. The circuits of the variouscontrol devices, as shown in detail in FIGURE 2, are completed through acontrol panel 13. A manual rheostat 14 is also connected thereto foradon the entry side of each stand, by load cells 17 and 13 mounted onthe stands so as to be afiected by the stretch thereof under load, or byshunts 19 and 2t) responsive to the current drawn by motors?) and 4.Whatever the.

source of the signal, it is' amplified and supplied to a control relayassociated with each stand, those for stands 1 and 2 being designated 21and 22, after a suitable time delay introduced by any convenient meansindicated at 21' and 22'. 7

FIGURE 2 shows the circuits of the speed-control system for motor 4indicated schematically in FIGURE 1. The motor of each succeeding standis provided with the same speed-control system. Control of the speed'ofmotor 4 is efiected by varying the excitation of its field' the windingof which, indicated at 23, is connected across an excitation bus 24, 24in series with rhcostat 6 and regulator 7. Regulator 7 has adilterential field 25 which normally tends to reduceits terminalvoltage, and acts to stabilize this voltage when excitation ismaintained by a main or control field winding 27 adapted to be connectedacross generator 5 in series with potentiometer 10. Regulator 7 has athird field winding 26 adapted to be connected across regulator 9 inorder to anticipate the speed levels to be controlled. Regulator 3 has adifierential stabilizing field winding 28 and a speed-anticipating fieldwinding 29 connected across the secondary of a transformer 39 theprimary of which is connected across generator 5. Regulator 9 has a mainor control field winding 31 connected across an excitation bus 32, 32 inseries with potentiometer 1t and rheostat 14. Currentlimiting resistorsare indicated in FIGURE 2 by blocks labeled R. The resistance elementsof the rheostats are similarly shown.

The speed-control system of FIGURE 2 is brought into play through theoperation of relays 21 and 22 and auxiliary relays shown in FIGURE 3which will be desig-.

nated specifically during the following explanation of the operation.Before a breakdown, reduced from a starting slab by the roughing stands,enters stand 1, the speeds of all the motors driving the finishingstands are adjusted to the proper values by operating rheostats 6, 6aand others similar thereto for each main drive motor such as 3 and 4.Rheostat 14 is also adjusted to effect a predetermined reduction in thespeed of motor 4 as the breakdown enters stand 1. This reduction isbrought about in a manner now to be explained.

When the mill is idling, motors 3 and 4 turn at their no-load speedsdetermined by the setting of rheostats 6.

on the setting of rheostat 14. Any difference between.

the voltage drop from 1411 to 5b and the drop from contact finger ltlaof potentiometer 10 to 51;, will appear across winding 31, contact 33aof a relay 33 being normally closed. This voltage will cause regulator 9to apply a voltage to motor 11, contact 33b of relay 33 being normallyclosed, in a direction such as to restore the balance between voltages10a, 5b and 14a, 5b. Thus these voltages are kept balanced until thespeed control is initiated.

As the breakdown enters-stand 1, relay 21 is energized after the lapseof a definite time, completing a circuit for relay 33 at contact 21a(see FIGURE 3). thereupon opens contacts 33a, 33b and 330 and closesThis relay 7 3,151, sea

contacts 33d, 33:: and a contact 33; in the circuit of the secondary oftransformer 3t initiating operation of the speed-control system toreduce the speed of motor 4. This results from the fact that thedifference between voltages 5a, 5b and i sa, 5b appears across winding27 whereupon regulator 7 adds an incremental voltage to increase thecurrent through motor-field winding 23, decelerating the motor 4. Theslowing down of motor 4- continues until voltage 5a, 5b is equal to thevoltage 190, 517.

While the speed of motor 4 is changing, the voltage applied to theprimary Winding of transformer 3% by generator 5 also changes and thisinduces a voltage in the secondary winding which is applied to winding29 The effect of the energization of winding 25? is applied by regulator9 to winding 26 of regulator 7 in such direction as to preventovershooting in the control of the speed or" motor 4 by winding 27 ofregulator 7 when relay 33 is energized.

Reduction of the speed of motor 4- is effected as explained above whilethe leading end of the breakdown is advancing from stand 1 to stand 2.On entering the latter the breakdown causes energization of relay 22which closes a contact 22a, energizing a relay 34 (see FIGURE 3). Relay34 opens a contact 34:: in the circuit of relay 33, deenergizing thelatter, whereupon it closes contacts 33a, 33b and 330 and opens contacts33a, 33a and 33 This takes the supplemental speed-control means formotor 4 out of operation. Relay 34 also closes a contact 34!) energizinga relay 35. Relay 22 also closes a contact 22b and brings into operationa similar speed-control means for the motor driving the third stand byenergizing a relay as and so on up to the sixth and last stand. Timers21' and 22, shown in FIGURE 2, are used to incorporate proper timingbetween the initiating signal and energization of relays 21 md 22 sothat the controls can be initiated at the proper instant with respect toposition of the leading or trailing end of a breakdown.

As already pointed out, the system of our invention not only deceleratesthe motors driving the several stands successively as the leading end ofa breakdown approaches them but also effects a similar speed adiustmeritas the trailing end leaves the preceding stand. After the initial speedadjustment, the motors return to their normal rolling speeds asdetermined by the settings of their rheostats 6 and 60. When thetrailing end of the breakdown leaves stand 1, relay 21 is deenergized,closing a contact 2117. A contact 35a having previously been closed byrelay 35, relay 33 is again energized and closes its own sealing circuitat contact 33g.

The second energization of relay 33 again brings into operation thesupplemental speed control means to reduce the speed of motor 4slightly, increasing the tension etween the second and third stands tocompensate for the loss of tension between the first and second. Whenthe trailing end of the breakdown leaves stand 2, relay 22 isdeenergized, opening the circuit of relay 34 at contact 22a.Deenergization of relay 34 opens the circuit of relay 35 at contact 3419and deenergization of relay 35 opens contact 351: deenergizing relay 33.This restores all the control elements for motor 4 to startingconditions. Contacts 39a and 395 are those of a relay similar to relays21 and 22, controlled by the entrance of the breakdown into the thirdstand. By this and other similar relays for the several stands, similarreductions of the speeds of the motors of stands three through fiveoccur successively as the trailing end of the breakdown proceeds throughthe stands. No reduction of the speed or" the sixth stand is necessarybecause no tension is possible after the strip leaves the fifth stand.The overall result, however, is that the system provides compensationfor the loss of tension at each stand individually as the trailing endleaves it, plus the reflected loss of tension between the fifth andsixth stands.

it will be apparent from the foregoing that our invention provides meanseffective to prevent excessive tension on the leading end of a breakdownas it enters successive stands of a continuous mill and to compensatefor loss of tension on the trailing end as it leaves successive stands.As a result, variations from desired gage in the portions of thefinished strip adjacent the ends are greatly reduced and a more nearlyuniform gage is maintained throughout the entire length or" the strip.The system is fully automatic and requires no attention when it has oncebeen installed and adjusted.

Although we have disclosed herein the preferred embodiment of ourinvention, we intend to cover as well any change or modification thereinwhich may be made without departing from the spirit or" the invention orthe scope of the appended claims.

We claim:

1. t continuous rolling mill comprising several mill stands arranged intandem, a motor for driving the rolls of each stand, a control for eachmotor for normally maintaining the rotation of the rolls of itsassociated stand at a predetermined substantially constant speed, asupplemental control for the motor or" the second stand to cause apredetermined reduction in the speed thereof, means associated with theihst stand and operable by the entrance of the leading end of abreakdown thereinto to operate the said supplemental control to decreasethe speed of the second stand only, and means operable after entrance ofthe leading end of the breakdown into the second stand to operate thesupplemental control to bring the motor of the second stand back to itsoriginal speed.

2. A continuous rolling mill comprising several mill stands arranged intandem, a motor for driving the rolls of each stand, a control for eachmotor for normally maintaining the rotation of the rolls of itsassociated stand at a predetermined substantially constant speed, asupplemental control for the motor of the second stand to cause apredetermined reduction in the speed thereof, means associated with thefirst stand and operable by the passage of the trailing end of abreakdown therebeyond to operate the said supplementm control todecrease the speed of the econd stand only, and means operable by thepassage of the trailing end of a breakdown from the second stand tooperate said supplemental control to bring the motor of the second standback to its original speed.

3. A continuous rolling mill comprising several mill stands arranged intandem, a motor for driving the rolls of each stand, a control for eachmotor for maintaining the rotation of the rolls of its associated standat a predetermined substantially constant speed, a supplemental controlfor the motor of each stand after the first to cause a predeterminedreduction in the speed of the associated motor, means associated witheach stand except the last and operable by the entrance of the leadingend of a breakdown thereinto to operate only the supplemental control ofthe next succeeding stand to decrease the speed thereof, and meansoperable after entrance of the leading end of the breakdown into thesaid next succeeding stand to operate the supplemental controlassociated therewith to bring the motor of the said next succeedingstand back to its original speed.

4. A continuous rolling mill comprising several mill stands arranged intandem, a motor for driving the rolls of each stand, a control for eachmotor for maintaining the rotation of the rolls of its associated standat a predetermined substantially constant speed, a supplemental controlfor the motor of each stand after the first to cause a predeterminedreduction in the speed of the associated motor, means associated witheach stand except the last and operable by the entrance of the leadingend of a breakdown thereinto to operate only the supplemental control ofthe next succeeding stand to decrease the speed thereof, means operableafter entrance of the leading end of the breakdown into the nextsucceeding stand to operate the supplemental control associatedtherewith to bring the motor of the said next succeeding stand back toits original speed, means associated with each stand except the last twoand operable by the passage of the trailing end ofthe breakdowntherebeyond to operate only the supplemental control of the nextsucceeeding stand to decrease the speed thereof, and means operable bythe passage of the trailing end of the breakdown from the last mentionednext succeeding stand to operate the supplemental control associatedtherewith to bring the motor of the last mentioned next succeeding standback to its original speed. 7

5. The continuous method of hot rolling a breakdown into stripcomprising passing the breakdown through a series of roll stands whiledriving each of the rolls at a predetermined normal speed and as thetrailing end of the breakdown reaches the rolls of a stand, temporarilydecreasing the speed or the ,rolls of the next succeeding stand apredetermined amount while maintaining each of the other stands at itsnormal speed to progressively reduce said trailing end to substantiallythe same gage asithe length of the breakdown preceding the trailing end,and returning the said next succeeding stand to its normal speed as soonas the trailing end of the breakdown passes from the said, nextsucceeding stand.

6. The continuous method of hot rolling a breakdown into stripcomprising passing the breakdown through a series of roll stands whiledriving each of the rolls at a predetermined normal speed and as theleading end of the breakdown reaches the rolls of a stand, temporarilydecreasing the speed of the rolls of the next succeeding stand apredetermined amount while maintaining each of the other stands at itsnormal speed to prog'ressily reduce said leading end to substantiallythe same gage as the length of the-breakdown following the leading endis reduced, and returning the said next suc-. ceeding stand to itsnormal speed when the said leading end reaches the said next succeedingstand.

7. The continuous method of hot rolling a breakdown into stripcomprisingpassing thebreakdown through a series of roll stands whiledriving each of the rolls at a predetermined normal speed and as theleading end of the breakdown reaches the rolls of a stand, temporarilydecreasing the speed of the rolls of the next succeeding stand apredetermined amount while maintaining'each of the other stands at itsnormal speed to progressively reduce said leading end to substantiallythe same gage as the length of the breakdown following the leading endis reduced, returning the said next succeeding stand to its normal speedwhen the said leading end reaches the said next succeeding stand and asthe trailing end of the breakdown reaches the rolls of a stand,temporarily decreasing the speed of the rolls of the next succeedingstand a predetermined amount while maintaining each of the otherstandsat its normal speed to progressively reduce said trailing end tosubstantially the same gage as the length of the breakdown preceding thetrailing end, and returning the said next succeeding stand to its normalspeed as soon as the trailing end of the breakdown passes from the saidnext succeeding stand.

8. In apparatus for controlling the operation of a first device having amotor and being operative with a strip of material and a second deviceoperative with said strip forpulling on the strip relative to said firstdevice, the combination of strip detector means operative with saidstrip at a predetermined location relative to one of said first andsecond devices for providing a first control signal when the strip isnot'present at said location,'motor op eration sensing means operativewith said motor for providing a second control signal that varies inaccordance with a predetermined operation of said motor, and a motorcontrol device operative with said motor and responsive to said firstcontrol signal for controlling the operation of said motor in accordancewith a predetermined value of said second control signal when the stripis not present at said predetermined location.

9. In apparatus for controlling the operation of a first device having amotor and a second device, with each of said devices being operativewith a strip of material for pulling on the strip to provide tension insaid strip between said first device and second device, the combinationof strip detector means operative with said strip at a predeterminedlocation relative to said first device for providing a .first controlsignal when the strip is not present at said location, operation sensingmeans operative with said second device for providing a second controlsignal that varies in accordance with a predetermined operation of saidsecond device, and a control member operative with said second deviceand responsive to said first control signal for controlling theoperation of said second device in accordance with said second controlsignal when the strip is not. present at said predetermined location.

. 10. In apparatus for controlling theoperation of at least alfirstdevice and a second device operative with a strip of material forperforming a predetermined operation relative to said strip, with eachof said devices being operative with said strip forpulling on the strip.

to provide tension in said strip between said devices, the combinationof strip detector means operative with said strip at a predeterminedlocation relative to one of said first and second devices for providinga first control signal when the strip is not present at said location,operation sensing means responsive to said first control signal andoperative with the other of said devices for providing a second controlsignal having a value that follows a predetermined operation of saidother device when said first control signal is not provided, and acontrol member operative withsaid other device and responsive to saidfirst control signal for controlling the operation of said other devicein accordance with a predetermined value of said second control signalwhen the strip is not present at said predetermined location.

11. In apparatus for controlling the operation of a first device and asecond device operative with a strip of material for pulling on thestrip to provide tension in the strip between said first and seconddevices, the combination of a temperature responsive strip detectordevice operative with said strip at a predetermined loca tion relativetoone of said firstand second devices for providing a first control signalin accordance with the temperature or" any strip present at saidlocation, operation sensing means responsive to said first controlsignal and being operative with the other of said first and seconddevices for providing a second control signal having a value that variesin accordance with a predetermined operation of. said other device andas long as said first control signal is not provided, and acontroldevice operative with said other device and responsive to said.

first control signal for controlling the operation of said other devicein accordance with a predetermined value of said secondcontrol signalthat is present when the strip detector device does not respond to thetemperature of any strip at said predetermined location.

12. In apparatus for controlling the operation of a first device and asecond device, with said first device.

strip present at said location, motor operation sensing means operativewith said motor for providing a second control signalthatvaries inaccordance with a predetermined operation of said motor, anda motorcontrol device operative with said motor and responsive to said firstcontrol signal for controlling the operation of said motor in accordancewith a predetermined value of said second control signal when the stripdetector means does not respond to the temperature of any strip presentat said predetermined location.

13. In control apparatus for a rolling mill including at least a firstdevice having a motor operative with a pair of roller members betweenwhich a strip of material may be positioned for performing apredetermined operation relative to said strip, and with said rollingmill including a tension controlling second device for pulling on thestrip relative to said first device, the combination with a stripsensing device for providing a first control signal when the strip isnot present at a predetermined location relative to said mill, a motoroperation sensing device operative with said motor for providing asecond control signal that varies in accordance with the operation ofsaid motor, and a control device operative with one of said first andsecond devices and responsive to said first control signal forcontrolling the operation of said one device in accordance with apredetermined function of said second control signal.

14. In control apparatus for a rolling mill including at least a firstdevice having a motor operative with a pair of roller members betweenwhich a strip of material may be positioned for performing apredetermined operation relative to said strip, and with said rollingmill including a tension controlling second device for pulling on thestrip relative to said first device, the combination with a stripsensing device for providing a first control signal when the strip i notpresent at a predetermined location relative to said second device, amotor operation sensing device operative with said motor for providing asecond control signal that varies in accordance with the operation ofsaid motor, and a control device operative with said first device andresponsive to said first control signal for controlling the operation ofsaid first device in accordance with a predetermined function of saidsecond signal.

15. In control apparatus for a rolling mill including at least first andsecond devices having a pair of roller members between which a strip ofmaterial may be positioned for performing a predetermined operationrelative to said strip, with said first device including a motor member,the combination with a strip sensing device for providing a firstcontrol signal when the strip is not present at a predetermined locationrelative to said second device, a motor operation sensing deviceoperative with said motor for providing a second control signal thatvaries in accordance with the operation of said motor, and a controldevice operative with said second device and responsive to said firstcontrol signal for controlling the operation of said second device inaccordance with a predetermined function of said second control signal.

16. in control apparatus for a rolling mill including at least first andsecond devices, with each of said devices having a pair of rollermembers between which a strip of material may be positioned forperforming a predetermined operation relative to said strip, and witheach of said first and second devices being operative for pulling on thestrip to provide tension in said strip between said first and seconddevices, the combination with a strip sensing device for providing afirst control signal when the strip is not present at a predeterminedlocation relative to one of said first and second devices, an operationsensing device operative with the other of said first and second devicesfor providing a second control signal that varies in accordance with theoperation of said other device, and a control element operative withsaid second control device and responsive to said first control signalfor controlling the operation of said second device in accordance with apredetermined function of said second control signal.

17. In control apparatus for a rolling mill including at least a firstdevice having a motor operative with a pair of roller members betweenwhich a strip of material may be positioned for performing apredetermined operation relative to said strip, and with said rollingmill including a tension controlling second device for pulling on thestrip relative to said first device, the combination with a stripsensing device for providing a first control signal when the strip isnot present at a predetermined location relative to said one of saidfirst and second devices, a motor operation sensing device operativewith said motor for providing a second control signal that varies inaccordance with the operation of said motor, and a control deviceoperative with the other of said first and second devices and responsiveto said first control signal for controlling the operation of said otherof the first and second devices in accordance with a predeterminedfunction of said second control signal.

References Cited in the file of this patent UNITED STATES PATENTS1,871,437 Winne Aug. 16, 1932 2,153,429 Millan Apr. 4, 1939 2,264,277Cook Dec. 2, 1941 2,287,851 Zeitlin June 30, 1942 2,342,767 Stoltz Sept.29, 1944 2,468,557 Huston Apr. 26, 1949 2,544,467 Michel Mar. 6, 19512,626,376 Harder Jan. 20, 1953

8. IN APPARATUS FOR CONTROLLING THE OPERATION OF A FIRST DEVICE HAVING AMOTOR AND BEING OPERATIVE WITH A STRIP OF MATERIAL AND A SECOND DEVICEOPERATIVE WITH SAID STRIP FOR PULLING ON THE STRIP RELATIVE TO SAIDFIRST DEVICE, THE COMBINATION OF STRIP DETECTOR MEANS OPERATIVE WITHSAID STRIP AT A PREDETERMINED LOCATION RELATIVE TO ONE OF SAID FIRST ANDSECOND DEVICES FOR PROVIDING A FIRST CONTROL SIGNAL WHEN THE STRIP ISNOT PRESENT AT SAID LOCATION, MOTOR OPERATION SENSING MEANS OPERATIVEWITH SAID MOTOR FOR PROVIDING A SECOND CONTROL SIGNAL THAT VARIES INACCORDANCE WITH A PREDETERMINED OPERATION OF SAID MOTOR, AND A MOTORCONTROL DEVICE OPERATIVE WITH SAID MOTOR AND RESPONSIVE TO SAID FIRSTCONTROL SIGNAL FOR CONTROLLING THE OPERATION OF SAID MOTOR IN ACCORDANCEWITH A PREDETERMINED VALUE OF SAID SECOND CONTROL SIGNAL WHEN THE STRIPIS NOT PRESENT AT SAID PREDETERMINED LOCATION.